Method of pickling metal articles



H. S. MARSH AND R. S. COCHRAN.

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-wi @@@m hn INVENTORS 5. I4/Hf H. S. MARSH AND H. S. COCHRAN. METHOD 0F PICKLING METAL ARTICLES. APPLicATIoN FILED MAR. 21, 1920.

LSQQYS., Patented Oct. 4, H2L

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WITNESS ES INVENTORS II. S. MARSH AND R. S. COCHRAN. METHOD 0F PICKLIIIIG METAL ARTICLES. APPLICATION FILED MAR. 27. 1920.

19392;?80, Patented Oct. 4, 1921.

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WTNESSES I |NVENTORS 74 WMW W553i 2; WM v Mir/@Lys Y* j 55,6%' I H. s. MARSH AND R. s. COCHRAN. METHOD 0F PICKLING `METAL ARTICLES. APPLICATION FILEDY MAR. 27, 1920.

1,39%?89. Patented 00A. A, 1921.

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HENRY S. MARSH AND RALF iS. COCHRAN, F YOUNGSTOWN, GEIQ.

METHOD 0F PICKLING METAL ARTICLES.

Specification of Letters Patent.

Patented Got. 4t, flgl.

Application filed March 27, 1920. Serial No. 369,173.

To all whom t may concern:-

Be it known that we, HENRY S. MARSH and RALF S. COCHRAN, residing at Youngstown, in the county of Mahoning and State of Ohio, both citizens of the United States, have invented or discovered certain new and useful Improvements in Methods of Pickling Metal Articles, of which improvements the following is a specification.

Our invention relates to the pickling of metallic articles, and, as we have developed it, it particularly concerns the pickling of sheet steel in the course of fabrication. As will be apparent, the invention in its broader aspects is applicable to pickling A metallic articles generally, Whatever be the shape or substance. The invention consists in improvements Vin method of pickling in continuous operation. The idea of pickling in continuous operation has been proposed before, but never to our knowledge has it been successfully carried out. Indeed, as heretofore proposed, a highly concentrated acid has been necessary, and for this reason alone these proposals have been impracticable.

The operation of our present invention may be successfully conducted in cordination with that of the continuous circulation of pickling solution, after the manner disclosed in our now pendingapplication for Letters Patent, filed January 9, 1920, Serial No. 350,383. Itneed not, of course, be co'- ordinated with this or any other particular system for maintaining the efficiency of the pickling solution, but, since we have so developed it, we shall here describe it in that cordination. Certain incidental features of sequence of the progress of the material unv der treatment, the several component pieces of apparatus. Fig.'II is a diagramlnatic view in side elevation of the scale breaker, in which the sheet steel is prepared for the pickling operation; Fig. III is a view .1n transverse vertical section, on the plane 1ndicated by the line III-IILF-ig. I, through the transfer-table and adjacent conveyer; Fig. -IV is a view in side elevation of this same transfer table in its relation to the conveyer; Fig. V is a view in transverse vertical section, on the plane indicated by the line V-V, Fig. I, of the pickling chamber and of the conveyer as related thereto; Fig. VI is a plan view, to smaller scale than Fig. V of pickling chamber and rinse cham ber; Fig. VII is a View in longitudinal vertical section, and to equal scale with Fig. WI, through pickling chamber and rinse chamber, the plane .of section being indicated by the line VII-VII, Fig. VI; Fig. VIII is a View in transverse vertical section, and to a scale somewhat larger still than that of Fig. V, through the drier, the plane of section bein indicated at VIII-VIII, Fig. I; Fig. I is a view in side elevation of the drier; Fig. X is a view in transverse vertical section through the discharge, the scale being somewhat less than that of Fig. V, and the plane of section will be found indicated at XX, Fig.

I. Fig. XI is aiview in side elevation of lXIII and XIV are views in transverse section and in side elevation of the pickling chamber, adapted to the incidental possibility of collecting the hydrogen gas gem erated in the picklmg operation. Figs. V and XVI are views in transverse section through thev pickling chamber, showin how certain of the machine parts of Fig. may be duplicated, with advantages which will be explained in the sequel.

The necessity for pickling steel sheets in the course of fabrication is universally known, and need not be dwelt on.

Beginning with the scale-covered sheet,

and before subjecting it to the pickling operation, we, in the practice of our invention,

peferably put it through a scale breaker. e may use as a scale breaker a machine of the sort commonly used for straightening sheets and plate, and such a machine will be used in the regular way-though ordinarily the degree of bending to which the sheets are subjected will, to satisfy our purposes, be greater than that ordinarily required when the machine is used for straightening.

. specially designed machine may be required,- to withstand the strain.

If the sheets to be, dealt with are heavy, a

The scale breaker is indicated-at 1, in Fig. I

`of the drawings, and Ain Fig. II, an ordinary sheet-straightening machine is diagrammatically shown, with a sheet advancing through it and undergoing the scale-breaking proc- .ess. The machine consists essentially' of a succession of positively driven rolls 11 (the number is not material) between which thesheet is warped, first in one direction and then in thelother. A'pair of rolls 12 at the receiving end of the scale breaker will bite upon the entering sheet and feed it between the sheet-bending rolls, while a second pair of rolls. 13 at the delivery end will flatten the sheet again and feed it forward to the next ensuing piece of apparatus.

The scale with which the sheet is coated is brittle, while the underlying steel is ductile, and the bending of the sheet first one Way and then the other will loosen 'the scale,

.so that much of it will drop ofi', and what remains will be to such extent. loosened that. in the ensuing piclrling operation the acid will the more readily work underneath and gain access to the steel. The rolls of the scale breaker may be, and preferably are, heated (as by. a flame applied beneath), to heat the sheets and so prepare them for the ensuing pickling operation.

The sheets are fed to the scale breaker one by one, by hand. In Figs. I and II, and elsewhere throughout the drawings, the arrows marked a indicate the direction of the advancing sheets.

From the scale breaker the sheets are delivered one by one to a table 3, Fig. I, more ullyillustrated in Figs. III and IV. The table 3 is so arranged that the sheet (A) delivered by the scale breaker will initiall rest upon it, in the full-line position indicated in Fig. III, in which the center'of gravity of the sheet lies beyond the edge of the horizontal portion ofthe table. The sheet will advance upon table 3 maintaining this position, until its rear edge passes from the rolls 13 of the breaker. Thereupon it will swing from the full-line position shown in Fig. III to the dotted-line position, and will slip down the apron 31 with which table 3 is provided and come to position in conveyer 4.

he conveyer 4 will be understoodbestl by comparing the showing of Fig. I with that of Fig. V. It consists of an endless liexible body member, in the form of a belt or chain, equipped with rollers 41 which travel in guide channels 42. It is so disposed that, throughout its Work-performing reach, it ex' tends through the succession of chambers presently to be described, and carries the sheets with which it then is laden through these chambers 4 one after another; while of the way. -Co`nveniently,. and as Shown,

'the idle, -return reach of the conveyer. is

above the work-performing reach, and the work carrying parts there assume inverted position.

The conveyer 4 is provided'with laterally extending arms 43, and from these arms fingers 44 extend.I Throughout the workperforming reach of the conveyer,'these ingers. stand vertically. They are arranged in pairs, and their tips may iiare divergently, to

insure the automatic reception of the sheets descending from table 3. The sheets come to rest inthe notch dei-ined by the successive pairs of lingers; the fingers engage the sheets at intervals on opposite sides, and support' them in edgewise standing' position as they are borne forward through the chambers. All this is clearly shown inthe drawings.

Throughout that portion of its path where it receives the sheets, the conveyer may rest upon a spring-backedbuier plate 45.

Those parts of the eonveyer which in the course of operation are exposed to acid, though vpreferably made of metal, ma be made of such acidfresisting materia as Monel metal or duriron (a lcast iron high in silicon).

The pickling chamber is indicated at 5,

Fig. I, and its particular constructionwill be understodon comparing Figs. V, VI, and VII. It is a long narrow chamber, surrounding the conveyer throughout a portion of its workfperforming.4 reach. The walls of the pickling chamber are preferably heat-insulating, and may conveniently be formed of wood. Within the chamber, and on either side ofthe path ofthe advancing sheets, is arranged a succession of spray nozzles, which conveniently take the form oi: vertically extending perforated pipes 51, hung at suitable successive intervals from mains or headers 52 above. The lower portionof the chamber constitutes a trough wherein a body of. acid B may accumulate. From this trough circulation pipes 53 communicate with the headers 52. -Pumps 54 are provided to maintain circulation.

At intervals throughout the length of chamber 5 the trough is dammed across by barriers 55. (Two such are shown in Fig. VI And it will be observed that these barriers subdivide the pickling chamber into distinct units, so far as concerns acid circulation, there being a separate circulation pipe 53 for each unit, and separate headers 52 for each unit. Communication is had from unit to unit by overflow of pickling solution, over the tops of the barriers.

Within the pickling chamber 5 near the at proper and convenient intervals.

of liquid in the trough, and underlying the conveyei arms 43, is a shelf 50. This shelf, though it may be continuous, throughout the length of the picklingA chamber, preferably is not so, but consists rather of a succession of disconnected boards over-hanging, each, one of the outlet openings from the trough through the circulation pipes 53. The solution dripping from the material under treatment would, but for this shelf, keep the body of solution B. agitated and the particles of scale 'in suspension, and these, carried through the circulation pipes, would tend to obstruct the spray' nozzles. The shelf by, its presence prevents agitation, and thus allowing the particles of scale to settle, insures a circulation of cleaner solution through the pipes 53 and the spray nozzles- The shelf is preferably discontinuous, to the end that the accumulated sediment of scale maymore readily be removed from the bottom of the trough. Such removal will occur Its functions, already indicated in part, are, in addition, to insure a more thorough mingling of the relatively enfeebled acid running? from the sheets under treatment with the relatively vigorous body of pickling solution B, to insure such a circulation through pipes 53 as will involve all the'body B of solution collected in the trough, and so to utilize the body ofsolution as a whole more fully and mo-re effectively than'would otherwise be the case, and, finally, to afford, if need be, a suport for the loaded arms 43 of the conveyer.

he upper surface of this shelf 50 is preferably gently inclined 'as shown downward from the walL of the chamber toward its free end. It will of course be suitably supported; in thisrespect the showing of Fig. V is diagrammatic.

To prevent a splashing out of the spray of pickfing solution, the wall of the pickling chamber may, where it is slotted to allow the entrance of arms 4:3 of the conveyer, conveniently be constructed as shown in Fig. V. The wall below stands farther out-the chamber is wider below1 than above; and the arm 43 of the conveyer may at the point of passage of the slot be inclined obliquely downward as shown, to the end that the vertical spacing of the margins of the slot may be diminished.

Acid is introduced to the trough in the bottom of the pickling chamber through a supply-pipe 56, arranged preferably at one end of the chamber 5, and advantageously at the remote or delivery end-the end from which `the sheets advance to the next stage of operation. The next chamber t which will presently be more fully described) is the rinse chamber. This rinse chamberis structurally a continuation of the pickling [chamber 5, and from a similar trough in its bottom rinse water flows over a barrier 57,

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similar to the barriers alreadydescribed, into the trough in chamber Through an vexhaust pipe 58 at the opposite end (the receiving end) of the pickling chamber, the pickling solution is led away. l 1

When the trough in the bottom ofthe chamber 5 is full of pickling solution, pickling may be effected upon sheets advancing through the chamber, by driving pumps 54, and so causing the solution to be sprayed through the pipes 5l upon the opposite surfaces of the sheets as they slowly pass across the paths in'which the spray is projected. The pickling solution running from the sheets falls back into the trough below.

lt will be understood that, water and supplies of fresh acid being supplied at one .end ofthe pickling chamber and spent pickling solution being drawn off at the other, the presence of the barriers 55 has this effect: that the pickling chamber is subdivided into clearly demarcated regions, and that in these successive regions the pickling solution is of diminishing strength and carries an increasing iron content, from inlet to outlet. Preferably (though not necessarily) the arrangement is that shown: The enteringr sheets are first sprayed upon by the solution at its weakest, and as they advance through the pickling chamber they receive solution of increasing strength, until at the end they are sprayed upon by'fresh solution. Certain economies of this preferred arrangement, in which solution and sheets under treatment advance in opposite directions, are obvious. There is this further, less obvious economy; the concentration of the copperas in solution toward one end of the pickling chamber leaves the pickling solution less contaminated elsewhere. The efficiency of the body of solution as a whole is thereby increased, and less refrigeration is subsequently necessary for the removal of the copperas and the reclaiming of the acid so# lution.

The acid suppliedthrough the supply pipe 56 is, as will presently be explained, preferably the reclaimed acid flowing from our improved reclaiming apparatus, to which reclaiming apparatus the spent acid flowing out atexit 58 is fed. This reclaimed acid is concentrated to a degree greater' than the' pickling operation requires. Hence the advantage of diluting it with rinse water from the rinse chamber. If with such an arrangement the solution in the pickling chamber is otherwise too weak, manifestly the inliow of acid may be enriched with additions ofmore highly concentrated acid. This matter will presently be considered further.

The acid preferably enters the trough in the pickling chamber at Aelevated temperature-the rinse water too is hot; the sheets, as has already been said, are preferably time.l

heated in the 'scale breaker; cie wang .o f the" Y for thecirculation pipes 53.

The rinse chamber 6y is, ashasbeensaid, continuous structurally with pickling-ch'amber 5. The interiorl arrangementis essen( tially the -same asl inV the pickling chamber and will be understood on comparing Figs.

.p V, VI, and VII.V Circulation pipesl63 are through spray pipes 61.- A `water-inlet is shown in Figs. VI. and VII, in which pumps 64 are arranged, through pipes -63- water passes to headers 62 whence' it is sprayed indicated at 66. In Athe rinse .chamber a circulation of. hot -water is mamtaineu,

Yrather than of pickling solution. -Under the spray of hot water' in the rinse-chamber the advancing. -sheets are washed free of acid,

l coals on a and from the rinse chamber the acid'ulated rinse water continually and gradually over-v flows into the piclding chamber. The rinse water will conveniently be condensed steam,

not :tarbelow the boiling pQint. v

Next in succession after -the rinse chamu ber stands the. drler, shown diagrammati' cally in Fig. I, in its 'place in the organization, and shown 1n its essential features ofconstructio'n in Figs. VIII' and IX. The drier is simply a chamber through which the now pickled and washed sheets pass, and in which condition of temperature and circulation are. such as to evaporate from the surfaces of the sheets the water withy which the surfaces are Wet. As shown in anexemplary way in Figs. VIII and IX,`this chamber is'long and "narrow, conforming in some degree 1n its shape to the pickling and drymg chambers; means of dicated, consisting in this case of a bed of .Y grate 71, a chimney 72 establishes draft to nourish the,`re and to carry away the waterA vapor as it forms. slot 1n the side wall to admit the arms 43 of the conveyer is arranged essentially as in. the plcklmg and rinse chambers, but it will be noted that, inasmuch as within chamber there is no spraying of liquid, the reason,

does not here exist for the widening of the chamber below and .introducing the conveyer arm ,in a direction `angularly downward; accordingly the slot cuts through an otherwise vertical wall disposed in a single substantial plane.4 l

The advancing conveyer carries the sheets one by' one through pickling chamber, rinse chamber, and drier in turn, and then to the discharge mechanism 8 (Fig. I), where the vsheets now pickled and ready for further treatment, are removed from the conveyer.

This discharge mechanism may take any rollers.

heating are in- The form desired. IVe have (in exemplary way,

so far 'as concerns'ourlbroader claims) shown a magnetic discharge mechanism, and. this4 Aweshall now describe, withpart-'icular ref-- erence to Figs. X and i I. l

Adjacent the path of advance of the sheets borne 1n conveyer-4 beyond drier?" and extending parallel 'with t atipath is a pair of struction of these rollersV need not be dwelt on; such rollers areon the market; their magnetic rollers 81. j The particular con-A characteristic features-are that, attracting different size.

- A guide 82 may be provided, to` bring the s an advancing sheet comes to o i sition .to be acted on, it automatically trips a make-and-break device 83,l and efectsfen,

advancing sheet 'to position adjacent 4the ergizing of the electromagnets of 'rollers 8 1, which up to that time had not been energized.

Immediately the rollers attract'the sheet,

and, as they continue to turn, they raisel the sheet from conveyer 4 and carry it over their upper surfaces. The -rising sheet advances I ice.

relatively-to the roller, so* that 4its forward This forward edge asses into a suitable guideway, convenient y formed by the mechanism to sheetsgoi"l -to their surfaces bodies orlrnedofl magnetic' Amaterial, by turning they convey such bod- .ies fromon'e point to another. The position of rollers 81 relatively 'to the path of' sheetv 'advance .is sufiiciently indicated in' the'dravw I ings, and the direction of rotation 'is .indicated by arrow c. Conveniently two-rollers A `85 edge projects farther and. farther from?y the,A roller.

opposite :lines of idle rollers 84. The mof -mentum of the sheet carries it forward (and.

its advance may be aided by gravity); the

`limitations, imposed -by the guidewaycause the sheet to break contact with rollers 81,

and the delivery is to any suitable.recepta cle. Fig. X shows a .crate 85 in' which has been stacked a' succession of sheets coming through the discharge mechanism. vAt. a.

point in its course where the magnetism ofl i rollers'Sl is no longer advantageous or de -sirable, the advancing sheet engages a sec ond trip 86, and, automatically swinging this trip, breaks the circuit and deenergizesagain the magnets ,of rollers 81. This leaves the rollers in condition; permitting the next advancing sheet to come to position opposite 4the discharge mechanism, and then a new shifting of trip 83 (which meanwhile has come to initial positioneither in cono sequence of the swinging oftrin 86 or`other wise) begins t-he operation anew. .It'will be understood that after each "operation trip- 86 resumes again its initial. position, either otherwise.

iac 1 .in consequence of the shifting of trip83 or;

iso

served that the conveyer, in traversing, in the direction indicated by the arrow a, so much of its path as is in dotted lines there indicated, is loaded with a succession of sheets, and that it carries these sheets through pickling chamber, rinse chamber, and drier, and inally in the discharging mechanism is relieved of its burden. So relieved, the conveyier returns upon itself, it being, as was initially explained, in form an endless belt or chain. The disposition of the return reach of the conveyer is suiiiciently indicated in Fig. V

Figs. XII-XVI illustrate various supplementary or variant features of structure, and may be briefly described.

In Fig. XII is shown in detail how a block 46 may be inserted between each pair of lingers 44C of the conveyer, to diminish the depth of the slot defined thereby, and to adapt the conveyer temporarily to sheets of smaller size than those primarily intended. These blocks will be secured by pins 47, passing through them and through tingers 44, to prevent falling out when the conveyer on its return reach is inverted.

Figs. XIII and XIV illustrate an adaptation of the pickling chamber for the recovery of the hydrogen the pickling operation. he slot in the chamber wall through which the arm 43 of the conveyer-extends is sealed by the liquid accumulating in the trough in the bottom of the chamber, the particular construction of wall and slot and conve er arm are clearly indicated 'in Fig. XII and the essential features will be taken in at a glance. No further description is necessary. i When hydrogen is to be-recovered, the ends of the pickling chamber will be closed, and the roo chimney 90 through which the hydrogen may be led of to suitable apparatus for collecting, drying, and compressing the hydrogen. Such apparatus is diagrammatically indicated at 91, Fig. I. As has just been said, the ends of the pickling chamber will in this case be closed, partially at least. The end walls may conveniently be made wholly or in part of sheet rubber, and through the -rubber slits may be cut to allow the passage of the conveyer. The bearing of the flaps formed by the edges of the slits 'upon the passing bodies will be eective, to

reduce to a minlmum circulatlon of gases,A

and vwill be found a practicable expedient to attain the endsin view. The conveyer,

which throughout the length of the pickling chamber dips below the surface of the reservoir of pickling solution B maintained in the bottom of the chamber, must pass over the end wall of the trough. To effect this, the guides 42 in which the conveyer runs are arched over the end walls of the trou h, as is illustrated in Fig. XIV. And, t at as generated in of the chamber will rise to a v the opening through the end walls of the chamber shall in the course of operation be kept as small and as tightly sealed as possible, the trough may be prolonged beyond the end walls of the chamber and the submersion of the conveyer in the solution in the trough (and, at the other end, the emerging of the conveyer) may be effected beyond the limits of the hydrogen-collectin chamber. This is indicated in Fig. XI To allow the conveyer to pass the barriers which extend athwart the trough at .intermediate points, the barriers themselves may be partially cut away. The barriers may be formed, so far as necessary, of such flexible material as sheet rubber, through which openings for passage of the conveyer may be formed. By such provision, as will be understood, the size of the openings through the` barriers, while suiiicient, will still be kept at a minimum..

Fig. XV indicates that a double line of plates may be carried on the succession of conveyer arms 43, and that within the pickling chamber and the rinse chamber the spray apparatus may be correspondingly doubled. It will be understood that, with this arrangement, two charging tables 3 will be provided, one on either side of the conveyer, and, correspondingly, at the point of discharge, duplicate discharging apparatus will be arranged on either side of the conveyer.

Fig. XVI indicates that the conveyer may be relieved of twisting strains by providing duplicate oppositely extending arms 43, and that the several parts of the apparatus shown diagrammatically in Fig. I and nowv described may be correspondingly duplicated, on either side of such a conveyer.

We remarked at the outset that apparatus of our invention for continuous pickling might be combined with a system for circulating the pickling solution in continuous cycle and relieving it at a suitable point in the circuit of the accumulating copperas (the product of pickling) and incidentally replenishing the acid content.4 Such a system is described in our pending application, filed January 9, 1920, .Serial No. 350,383. Indeed, in such a combination itself lie specific features of invention. It remains now to follow the course of the circulating pickling solution, and to indicate to what treatment it is subjected, and in what apparatus.

We shall begin with the spent solution emerging from the pickling chamber through orifice 58, Fig. VII. The solution as it here emerges is, for pickling purposes, relatively weak and ineffective. A large part of the sulfuric acid which the solution carried when it entered the pickling chamber has reacted with the iron of which the sheets are essentially composed, and been converted into copperas, and this coppelfas has continued in solution, enfeebling the solution .by its formation, and tendingY by its presence in solution to render the enfeebled acid stillless effective than otherwise it would be. The.` solution emerging then through orifice 58 is a relatively Weak solution of'sulfuric acid in Water, carrying also 'in solution a substantial burden of copperas.

acid (ordinarily'of 60% purity-possibly as high as 66%) as are requisite to bring the reclaimed acid to the proper strength for re-introduction in continuous operation to the, pickling chamber again. The reason for adding the acidat this point will presently be explained; herein is a feature of invention with us. An acid storage tank 93 is indicated, from which acid may flow to tank 92 in such measured quantities and with such continuity or at such intervals as may be desired.

From tank 92 the acid, now strengthened but` still carrying its burden of copperas is pumped by a pump 94 to reclaiming apparatus 95. This reclaiming apparatus need not here detain us; it is fully described in our application alluded to. In it the circulating stream of solution is by means of vcooling and agitation freed of the copperas. The crystallized copperas wet with acid solution is carried to a centrifuge 96, Where the acid solution is separated and returned to the line throu h Which the reclaimed acid solution is delivered from the reclaiming apparatus to flow to the pickling chamber. cumulated mass of copperas crystals may While still in the centrifuge, be rinsed in Water land then removed, in condition sufficiently free from acid and sufficiently dry to be marketable.

We here interrupt the description to give explanation of a refinement in the reclaiming operation. It has just been remarked that there isadvantage in making the additions of fresh acid before the removal of the copperas. We find that, by so increasing the acid strength of the solution still carrying the copperas, the copperas may be removed much more rapidly and much'more completely than otherwise.

From the reclaiming apparatus the acidv passes, on its way back tothe pickling chamber, .through a heater 97, to restore its heat and brin it again to a temperature of say 200' F. Ifrom the heater the acid enters the pickling chamber through the orifice 56 and it there isdtluted to working strength by This may be merely a4 The ac-.'

4mingling with the Water coming from'the rinse chamber over barrier 57.

A few incidental matters require further mention. First, the matter of temperature. The pickling operation is conducted at relatively high temperature, about 200 F.' The spent pickling solution is hot and it enters the reclaiming apparatus at a temperature not far below 200. There, as is explained in our co-pending case already alluded to, a portion only (and that a relatively small portion) 'of the heat is lost, for by suitable heat transference the liquid, first chilled to remove the copperas, is, before it passes on,

heated' again. In the heater the `minimum loss necessarily incident to reclaiming is restored, and the reclaimed and strengthened solution renters the ickling chamber at the temperature of picklmg. It has been noted in the progress ofthe specification that the sheets are heated in preparation for pickling,

and that the rinse Water, which in the' pickcommonly conducted hydrogen recovery is practically impossible. In' the practice of our. invention it becomes Wholly practical, and indeed very simple.

lBy virtue of the spray system now described acting upon the continuouslyaadvancing succession of sheets, it will be observed that each sheet in turn passes beneath a succession of sprays and that While these sprays are of different degrees of purity and intensity so far as concerns acid content, there is one spray, preferably the last in the succession which the sheet encounters, in

. which the sprayed-on solution is practically free of copperas. We preferably, in the performance of the operation, so proportion the supply of components that the solution at this point shall be relatively high in its acid content, that is to say high as compared with the acid content of pickling solutions generally, and We maintain it at high temperature, near the boiling point. The conjoint effect of all of these provisions: (l) the initial loosening of the scale; (2) the application of the solution by spray; (3) the consequent continual Washing away of the loosened scale; (4) the d s ,ubjecting of every ict area ofthe surface of the article to a continually fresh stream; (5) the high temperature due to preheating of the sheets and preheating of the solution; (6) the Washing 139 ascenso when sheets are taken from the solution' which is too hot, they emerge coated with an objectionable black deposit. This black coating is formed after the scale is removed and while the sheets remain still in the pickling bath. By removing the sheets from the action of the pickling solution immediately on the disappearance of the scale (the time of operation may be regulated by controlling the speed of the conveyer, to meet any condition), and by carrying the sheets immediately, as .soon 'as pickling is completed, directly from acid sprays to water sprays, and then bringing them progressively into a drying chamber, the development of such a black deposit is prevented.

We have in the foregoing specification described in some detail a number of pieces of associated apparatus and the mode of operating them. Much of this showing is exemplary, and our invention is by no means confined to an exact following of such in- VGi() struction. ln the ensuing claims we define the essence of our invention, and so long as this be present, our invention will be practised, regardless of whether the minute description given be adhered to or not.

We claim as our invention:

1. A step in a method of removing in continuous operation scale from the surface of a succession of metallic articles which consists in causing the articles to advance in succession through a spray of hot pickling solution.

2. A step in a method of removing laminate scale from the surface of a sheet of metal which consists in subjecting the sheet while maintained in verticalwposition to sprays of hot pickling solution directed upon its side.

3. A method of removing scale from the surface of'a metallic article which includes, first, heating the article, and then vcausing a spray of hot pickling solution to play upon its surface. l

4. A method of removing from the surface 0f a flexible metallic r,article laminate scale, which consists in, first., v loosening the scale by bending the article, and then subjecting the article to the action of a spray of hot pickling solution.

5. The herein described method of pickling metal articles which consists in subdividing a stream of. pickling solution into communicating portions, causing the liquid of each portion to circulate through a spray,

and causing the article to be pickled to pass through the sprays of the successive portions.

6. The hereln described method of plekling metal articles which consists in drawing pickling solution from a flowing stream at successive points and projecting it in a succession of sprays and causing the articles to be pickled to advance through vthe sprays in a direction countercurrent to thestream.

7. The herein described method of pickling metallic articles which consists in causing them to advance through a closed chamber, maintaining within the chamber a spray of pickling solution, and at the same time collecting the gas accumulating in said chamber in consequence of the pickling reaction.

8. The herein described method of pickling metal articles which consists in causing the articles to advancein a determined path, causing pickling solution to circulate in a closed cycle which shall in part intercept the pathway of the articles to be pickled, causing the circulating solution to form a spray in that part of its cycle where it intercepts the pathway of the articles, and subjecting the solution elsewhere in its cycle to a reclaiming operation.

9. The herein described method of pickling metallic articles including the circulation of a stream of pickling solution in closed cycle through a pickling chamber, subjecting theJ circulation solution in the course of the cycle to a reclaiming operation, and introducing into the circulating stream fresh raccessions of acid and of water.

10. rl`he herein described method of pickling metallic articles which consists in maintaining a succession of sprays, causing water to spray through the first of these sprays and the same water mingled with acid subsequently to spray through another of said sprays and causing the article to be treated to advance through such sprays countercurrent to the course of liquidindicated.

11. The herein described method of pickling metallic articles which consists in causing pickling solution to circulate in closed cycle through a pickling chamber, adding to the stream emerging from the pickling chamber fresh supplies of acid, and after such addition subjecting the pickling solution in its further circulation to a reclaiming operation.

l2. The herein described method of pickling iron articles which consists in causing a solution of lsulfuric acid to flow over the articles to be treated, adding to the stream of acid solution at a point beyond that where it washes the articles under treatment, new supplies of acid, and, at a point still farther on inthe stream, subjecting the solution to a copperas-precipitating operation.

13. The method herein described of pickling iron articles which consists in subjecting a succession of articles to a spray of pickling solution of constantly maintained quality, high in vacid and low in copperas, and at elevated temperature.

and subjecting them successively and on both 1 y5 .sides to a spray of pickling solution of con- Witnessesz- B i. f l 1,392,780

,14. The method hereindescribed of pickvIn testimony whereof We have hereunto ling sheet steel whichconsistsl in maintainset our hands. ingsl a succession of sheets in'vertieal position .HENRY S. MARSH.

RALF S. COCHRAN.

stantlymaintamed quality, high in cid and LEO VPURGELL,

low in c opperas, and lat elevated temperature. CARL- ANTHONY. 

